Chemical Quantities

Outline Moles Molar Mass Empirical Formula Molecular Formula Percent Composition

Moles Unit for a set number of representative particles. 6.022X10^23 atoms to be exact (Avogadro’s number) Used in chemical equations to relate the amounts of each element or molecule.

Molar Mass One Mole is equal to the atomic mass of an element in grams. For example: Carbon has an atomic mass of 12.01, this means that Carbon has a molar mass of 12.01 grams.

Empirical Formula Smallest whole number ratio of the atoms in a compound. For instance, Ca2O2 has an empirical formula of CaO

Molecular Formula Same as empirical formula, or simple whole number ratio of empirical formula Both are the same for most simple compounds like water, and CO2 Are often not same for complex compounds like C3H6

Percent Composition Shows what percent of a substance is composed of a specific substance. For example, in 80/20 hamburger meat, 80% of it by mass is actually meat, whereas the other 20% is fat. With elements, you work with the molar masses. For H2O we know the molar mass is ~ 18 grams/mol For Hydrogen 2 grams/18 grams*100 = 11.11 % For Oxygen 16 grams/18 grams*100 = 88.89%